[Tagging] River crossing grade

[Andrew Harvey]

On Fri, 28 Jan 2022 at 00:44, Peter Elderson <pelderson at gmail.com> wrote:

> I don't see much added value in this proposal.
> Boat is not applicable (not a ford), use ferry for that: established
> tagging.
> Swimming, not a ford.
> Stepping stones, I think then it's still a ford; established tagging.
> Add depth, width as needed. An estimate will suffice. Dry=0 cm, soles=5
> cm, ankle=10 cm, knee=0,5 m, wade=1 m.
> Intermittent, tidal: there is tagging for that.
> Construction key could help if you want to tag an artificial ford.
>

The proposal never mentions boating or ferrying, that's a tangential issue.
Similarly it never says that swimming across must be defined as a ford=yes,
and I'm not proposing to change stepping_stones, nor proposing to change
the existing intermittent or tidal tags. It's narrowly focused on waterway
crossings by foot and the likely water depth you'll encounter. the
construction tag or lifecycle prefix is for things "in construction" not
"constructed" features. I'm not proposing to change the existing depth or
width tags either, rather proposing instead of needing to precisely survey
in metres, you can tag based on these easy to survey and easy to data
consume values.

On Fri, 28 Jan 2022 at 02:01, Sinus Pi <sinus+osmtag at sinpi.net> wrote:

> How about a different approach to the stepping stones...
>
> What do you call a (usually, but not always) man-made structure that
> allows you to cross a waterway dry-footed? A bridge.
> Is a plank thrown over a stream a bridge? Likely.
>

Yes, bridge=yes + bridge:structure=beam + handrail=no + width=X.
Potentially using bridge=plank.


> Is a log fallen over the river, now commonly used as a crossing, a bridge?
> Kind of.
>

While it can act like a bridge I would not tag it as such, usually a fallen
log would need either a lot of balance or you to sit and shuffle along,
quite different to a bridge. The surface would usually be round and many
people may struggle. If the fallen log had been transformed into a bridge
like by flattening the top or nailing in rungs, then maybe you could tag it
as a bridge.


> Is a stone chucked into the river a bridge? Well... why not?
>

I wouldn't say so. If they are commonly used by most people crossing the
river I'd tag based on my proposal about how wet you'd get using them.

Hence: why not bridge=stepping_stones?
> And leave ford=* for where the waterway cannot (usually) be crossed
> without getting your feet wet?
>

I'll sidestep that question because my proposal isn't about
changing/tagging bridge or ford, it's only about how wet you'll get when
you have to go through the watercourse.

On Fri, 28 Jan 2022 at 02:30, Philip Barnes <phil at trigpoint.me.uk> wrote:

> Stepping stones are not a bridge, any more than they are a ford, although
> that has been in use a long time.
>
> Why not highway=stepping stones, in the same way we have highway=steps.


Sounds reasonable as a separate proposal.



On Fri, 28 Jan 2022 at 04:21, Tod Fitch <tod at fitchfamily.org> wrote:

> In the semi-arid area that I live and do a lot of hiking we don’t have
> many year round streams. Most are either seasonal or have ephemeral flows.
>
> Focusing on the trails that cross the few year round streams, every single
> water crossing on them changes fairly often either due to changes in flow
> or attempts by various hikers to create a way to get across without getting
> their feet wet. For any give crossing, if it has been more than a few days
> since you last visited, you will not know what you will find. You may find
> some branch has been dropped into the water that you can balance on, a
> couple of weeks later that has washed away but someone had thrown in some
> large stones you can use, another time you find the flow channel has
> changed and you can leap across, and the next time all that is washed away
> and you are reduced to wading.
>
> My point being that flowing water and hikers are both dynamic and if you
> are getting to the point where you are trying to tie it down to “stepping
> stone”, “fallen log”, “step over”, etc. then in my area you are doomed to
> remap the crossing every couple of weeks and a person using a map or app
> that doesn’t update every day is likely to find a different situation on
> the ground than OSM has told them. From a practical point of view for
> mapping in my area there is really only a few values I might be able use
> that are stable:
>
> “You area almost certainly going get your feet wet”
> “There is a pretty good chance you will get your feet wet”
> “You are very likely going to be able to keep your feet dry”
>

I'm not sure the best way to deal with seasonal or ephemeral flows. You
could perhaps use the seasonal values as suffixes:

water_crossing_level:foot:seasonal:wet_season=swim
water_crossing_level:foot:seasonal:dry_season=wet_soles

For ephemeral or intermittent flows could the :min and :max suffixes work?

The main tag makes more sense and is easier when flows don't change too
much. All the ones I can think of are consistent for 99% of the time,
unless you're out during a heavy storm. I understand some places it might
be too hard to tag this, but I don't think that warrants never using the
tag for places where it's usually consistent.

If you're relying on some branch or stones that usually get washed away I'd
tag assuming those aren't there, and then if they are it's a bonus for you.


> But if you insist in going into the weeds with a multiple values that are
> temporally dependent, you should also consider places where there are
> prefabricated bridges that are stowed during the off (rainy season) and
> then assembled during the dry summer hiking months (I have seen several of
> these in the redwood forests of northern California). Are they fords, yes
> for about 1/2 the year. The other half there is a bridge there.
>

The conditional tagging might help out with that.


> And then there are stream crossings in the higher mountains that are
> trivially crossed on skis in winter or by wading in summer and autumn but
> if you attempt them at all during spring melt you are basically committing
> suicide.
>

Maybe some combination of conditional tagging and :season suffixes.


> Sorry for being a curmudgeon here, but it seems to me that trying to get
> more detailed than a general “there be a water crossing here without boat
> or bridge” (i.e. ford=yes) is doomed to failure.
>

It's up to you if you think tagging it makes sense and is useful then you
could, but if you think there's too much variance then you could just not
tag it.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tagging/attachments/20220128/69d33e92/attachment-0001.htm>