вс, 3 февр. 2019 г. в 16:38, Paul Allen <pla16...@gmail.com>:
> Yes, we could switch to calling them all drains and then adding > lined=yes/no, but we already > have ditch and drain. I think it's better to fix the wiki than do that. If it was to select just one tag for the two notions, I would choose "ditch", not "drain". Most of ditches are drainage ditches, hence usage=drain can be assumed by default if not defined, but renaming irrigation ditches into drains+usage=irrigation sounds incorrect. Cheers, Eugene вс, 3 февр. 2019 г. в 16:38, Paul Allen <pla16...@gmail.com>: > On Sun, 3 Feb 2019 at 10:53, Eugene Podshivalov <yauge...@gmail.com> > wrote: > >> >> There are distinctions between these two terms, otherwise they would not >> be defined separately. >> In simple words, a ditch is a small open-air man-made or self-formed >> channel in the ground for absolutely any purpose, both lined or unlined >> entirely or partially. >> > > Ummmm, maybe. Maybe not. > > Part of the problem, of course, is that English dictionaries are > descriptive, not proscriptive: > if words are misused in English frequently enough, that misuse becomes one > of the word's > meanings (which is why "cleave" is its own antonym). The fact that > "ditch" and "drain" are > often used interchangeably these days doesn't mean that there isn't a > meaningful > distinction. > > See https://en.wikipedia.org/wiki/Ditch and > https://english.stackexchange.com/questions/190527/difference-between-ditch-trench-and-gutter > - a ditch is a simple, unlined trench for the purpose > of drainage or irrigation. A salient characteristic is that it is > unlined. It is used to drain (mainly) > agricultural fields with a high water table. The fact that it is unlined > means that water can seep > through the side of the ditch and then flow away. A lined ditch would not > work (only water above > the lining could seep into the ditch rather than across the whole height > of the ditch). Irrigation > is the same thing in reverse - a lined ditch wouldn't work as well. > > A drain is lined to *prevent* seepage. At its smallest, it is a roadside > gutter (open drain) which > usually has frequent openings to underground drains. Or it may be a small > channel. The > distinction between a drain and a canal is one we can spend months arguing > about. :) > > From everything said here and everything I've found on the internet I'd > say that lined/unlined > is the only distinguishing characteristic between ditch and drain. Size > is irrelevant. There > is a real difference in purpose and on-the-ground appearance between a > channel > designed to allow seepage to/from the land it passes through and one that > is not. > > Yes, some mis-tagging is inevitable. If you're using aerial imagery it's > hard to tell if > something is lined or unlined. Or even if it's part of a stream that has > been artificially > straightened. But you can make a fairly good guess in most instances. We > also have > to acknowledge that we rarely achieve perfection but do the best we can > and hope any errors > are corrected later. If we throw away the distinction (they're all > drains) it will be harder to > fix than if we keep the distinction and realize that there will be > occasional errors. > > Yes, we could switch to calling them all drains and then adding > lined=yes/no, but we already > have ditch and drain. I think it's better to fix the wiki than do that. > > -- > Paul > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging >
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