[Tagging] Additional detail of Levee mapping via embankments

[John Willis]

> On Nov 11, 2019, at 6:15 PM, Martin Koppenhoefer <dieterdreist at gmail.com> wrote:
> 
> I agree we should have a way to map both limits, upper and lower, for all kind of similar features, e.g. embankments, slopes, and similar.


> On Nov 11, 2019, at 7:40 PM, Volker Schmidt <voschix at gmail.com> wrote:
> 
> I have stood in front of these large levees that prevent big rivers from flooding the surrounding country side many times her in Italy and did not find a suitable tagging for both the top and the bottom border lines of the object.



I think it is pretty easy to make a  “lower bounds” way or area (or both) that compliments the existing man_made=embankment way.  

To me, the problem is levees. After having mapped many KM of levees (incorrectly), it is really really nice having the two pairs of embankments make up the two halves of the levee, because it is easier and more flexible to map the two slopes (which widen and narrow, split & merge, and disappear for short sections), rather than trying to assume that the man_made=dyke centerline way accurately shows the the “top” of the levee. the top varies by width from something easily represented by way to something 50m wide in some places (as linked to earlier). The =dyke way should represent the inner-most extent of the high point of the levee (if it has a weird bulge in the top). 

I made 2 sections of mapping examples on a simple section of levee along the Tone River that has a levee breach repair station on top, so the levee is wider here than normal. (for a short time).  


a man_made=dyke (on the cycle path) with:


- two pairs of embankment lines   ( man_made=embankment + man_made=embankment_lower ) with a regular grass polygon sandwiched between it.


- Two regular embankment lines along the top with an area:man_made=embankment polygon representing the slope (also tagged with grass). 

https://www.openstreetmap.org/edit#map=17/35.97777/139.89482 <https://www.openstreetmap.org/edit#map=17/35.97777/139.89482> 


Do you need a relation on them? 

Any suggestions on improvements? 

Javbw
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