[Tagging] Additional detail of Levee mapping via embankments

Richard ricoz.osm at gmail.com
Tue Nov 12 22:10:46 UTC 2019

On Wed, Nov 13, 2019 at 07:04:42AM +1000, Graeme Fitzpatrick wrote:
> On Wed, 13 Nov 2019 at 05:05, Richard <ricoz.osm at gmail.com> wrote:
> >
> > We need new tags for the bottom of embankmets, top of cuttings, bottom of
> > cliffs, earth_banks
> > and maybe a few others if we want to map them.
> >
> > Imho all those should be tagged ways such as cliff:base, relations could
> > be used optionaly
> > to relate a particular cliff edge to a particular cliff base which would
> > define the
> > area of the slope.
> >
> > Here is what I see:
> > * man_made=embankment_base or man_made=embankment:base
> > * man_made=cutting or man_made=cutting:top - top edge of cutting in
> > analogy to
> >   man_made=embankment (126 pieces in database but straightforward to
> > extend)
> > * natural=cliff_base or natural=cliff:base
> > * natural=earth_bank_base or natural=earth_bank:base
> >
> Just a thought - how about a new area tag to show the "sides" of these
> features, something like natural=slope?

natural=slope could be somewhat misleading.. people would map all kind of 
other slopes.

Could be natural=cliff:area ?
However because embankemnt:area would be very misleading, it would have to 
become  man_made=embankment_slope:area ?

> You have your line to mark the top edge of the cliff or embankment, then
> mark the visible area of the wall / side / bank down to it's base as the
> =slope, which would be much simpler than mucking around with relations
> (which I, & apparently quite a few others, don't really understand?)

should not have even mentioned the relations, not a big fan of them either;)

So it boils down to either
* mapping the slope area
* mapping the upper and/or lower bounds of the slope area

Depending on case the one or other possibility may be better but I am not
sure they can be used together.

My feeling is that simple tagged ways (that is top and bottom edge) are more 
flexible and scale better to complex cases than areas.

> Could also have height to say this bank is 5m tall; normal land cover tags
> would apply to say it's grass, scrub, bare rock etc; incline to show it's
> at 45° & so on.

We have all this already? In my experience adding height=XXX to natural=cliff 
ins't very useful. The height (or width) varies along the cliff.

> Would also be nice if it rendered, perhaps as either fine diagonals or
> cross-hatching (of course, the ideal would be if it rendered like map
> contour lines - on a gentle slope the lines are wide apart, getting
> narrower together as it get's steeper :-))

we have other methodes for countour lines
> & when I've just had a look, natural=slope has actually been used 1466
> times, https://taginfo.openstreetmap.org/tags/natural=slope#overview,
> despite being undocumented - searching the wiki for "slope" takes you to
> the "incline" page https://wiki.openstreetmap.org/wiki/Key:incline, which
> appears to for intended for roads?

wondering what those slopes mean?


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